Ok Google, how big is a light-year?

Published by Jason McCampbell on November 23rd, 2016

Last summer I was sitting outside on the deck at night working and, while waiting for a build, I was looking at the stars. Then I got curious is how big a is light-year? Ok, I can look it up and it's ~5.9 x 10^12 miles. So more miles than the US Government's annual budget in dollars. I can't comprehend either.

At the time I started playing with Google searches, but I wanted to try using only Google Assistant through voice commands.

"Ok Google, how big is a grain of sand?": Sand ranges in size from 2-64mm. Close enough, call it 1mm for really fine sand.

[Edit: I misunderstood Google or misread the Wikipedia entry: 2-64mm is the range for gravel, and sand is smaller than that. So 1mm for sand is coarse sand. Thanks, Johnathan, for the correction.]

"Ok Google, what is the diameter of the Earth in millimeters?": 12.742 x 10^9 mm. There's our scale factor.

"Ok Google, how big is a light-year in millimeters?": 9.461 x 10^18 mm.

"Ok Google, calculate 9.461 / 12.742": 0.743 x 10^9 or 743 million. Doing 18-9 in my head is easier than trying to figure out how to speak the parens to Google.

"Ok Google, convert 7.43 x 10^8 mm to miles": 461.7 miles. This took a couple of tries and I had to phrase it this way. Using "743 million millimeters" seemed to confuse it. But there we have it, if the Earth was 1mm in diameter, one light-year is 462 miles, about an 8 hour drive by car.

"Ok Google, what is the nearest star?" It correctly said Alpha Centauri is the nearest neighbor to the Sun.

"Ok Google, how far is Alpha Centauri?": 4.367 light-years from Earth

"Ok Google, calculate 4.367 * 462": 2017 (miles).

"Ok Google, how far is it from Austin, TX to Boston, MA?" 1956.7 miles driving distance.

So there we have it. If the Earth was 1mm in diameter, a little smaller than fine sand, the nearest star system, Alpha Centauri, is about the distance from Austin to Boston with a few detours to get food and charge the batteries. That's a long trip.